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in creator/contributor: "Hammons, B.E."

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Origin of the Time-Dependence of Wet Oxidation of AlGaAs

The time-dependence of the wet oxidation of high-Al-content AlGaAs can be either linear, indicating reaction-rate limitation, or parabolic, indicating diffusion-limited rates. The transition from linear to parabolic time dependence can be explained by the increased rate of the formation of intermediate As{sub 2}O{sub 3} vs. its reduction to elemental As. A steadily increasing thickness of the As{sub 2}O{sub 3}-containing region at the oxidation front will shift the process from the linear to th… more

Date: February 15, 1999

Creator: Allerman, A. A.; Ashby, C. I. H.; Bridges, M. M.; Hammons, B. E. & Hou, H. Q.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

InGaAsN Solar Cells with 1.0eV Bandgap, Lattice Matched to GaAs

The design, growth by metal-organic chemical vapor deposition, and processing of an In{sub 0.07}Ga{sub 0.93}As{sub 0.98}N{sub 0.02} solar Al, with 1.0 ev bandgap, lattice matched to GaAs is described. The hole diffusion length in annealed, n-type InGaAsN is 0.6-0.8 pm, and solar cell internal quantum efficiencies > 70% arc obwined. Optical studies indicate that defects or impurities, from InGAsN doping and nitrogen incorporation, limit solar cell performance.

Date: November 24, 1998

Creator: Allerman, A. A.; Banas, J. J.; Gee, J. M.; Hammons, B. E.; Jones, E. D. & Kurtz, S. R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Novel InGaAsN pn Junction for High-Efficiency Multiple-Junction Solar Cells

We report the application of a novel material, InGaAsN, with bandgap energy of 1.05 eV as a junction in an InGaP/GaAs/InGaAsN/Ge 4-junction design. Results of the growth and structural, optical, and electrical properties were demonstrated, showing the promising perspective of this material for ultra high efficiency solar cells. Photovoltaic properties of an as-grown pn diode structure and improvement through post growth annealing were also discussed.

Date: March 26, 1999

Creator: Allerman, A. A.; Chang, P. C.; Gee, J. M.; Hammons, B. E.; Hou, H. Q.; Jones, E. D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Wet oxidation of Al{sub x}GA{sub 1-x}As: arsenic barriers on the road to mis

Three characteristic regimes were identified during wet thermal oxidation of AlxGa(1-x)As (x=1 to 0.90) on GaAs: oxidation of Al and Ga in the alloy to form to an amorphous oxide layer, formation and elimination of elemental As and of amorphous As2O3, and crystallization of the oxide film. Residual As can produce up to a 100fold increase in leakage current and a 30% increase in bulk dielectric constant. Very low As levels produce partial Fermi-level pinning at the oxidized AlxGa(1-x)As/GaAs int… more

Date: February 1, 1997

Creator: Ashby, C. I. H.; Sullivan, J. P.; Newcomer, P. P.; Missert, N. A.; Hou, H. Q.; Hammons, B. E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Novel Metal-Sulfur-Based Air-Stable Passivation of GaAs with Very Low Surface State Densities

A new air-stable electronic surface passivation for GaAs and other III-V compound semiconductors that employs sulfur and a suitable metal ion, e.g., Zn, and that is robust towards plasma dielectric deposition has been developed. Initial improvements in photoluminescence are twice that of S-only treatments and have been preserved for >11 months with SiO{sub x}N{sub y} dielectric encapsulation. Photoluminescence and X-ray photoelectron spectroscopies indicate that the passivation consists of t… more

Date: August 9, 1999

Creator: Ashby, Carol I.H.; Baca, Albert G.; Chang, P.-C; Hafich, M.J.; Hammons, B.E. & Zavadil, Kevin R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

In-situ optical photoreflectance during MOCVD

This report summarizes the development of in situ optical photoreflectance as a tool for measuring impurity concentrations in compound semiconductors. The authors have successfully explored the use of photoreflectance as an in situ tool for measuring n-type doping levels in metal-organic chemical vapor deposition (MOCVD) grown GaAs materials. The technique measures phase and frequency shifts in Franz-Keldysh oscillations measured on uniformly doped thin films. Doping concentrations from 5 {time… more

Date: January 1, 1998

Creator: Breiland, W.G.; Hammons, B.E.; Hou, H.Q. & Mei, X.B.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

In-situ spectral reflectance for improving molecular beam epitaxy device growth

This report summarizes the development of in situ spectral reflectance as a tool for improving the quality, reproducibility, and yield of device structures grown from compound semiconductors. Although initially targeted at MBE (Molecular Beam Epitaxy) machines, equipment difficulties forced the authors to test most of their ideas on a MOCVD (Metal Organic Chemical Vapor Deposition) reactor. A pre-growth control strategy using in situ reflectance has led to an unprecedented demonstration of proc… more

Date: May 1, 1997

Creator: Breiland, W.G.; Hammons, B.E.; Hou, H.Q.; Killeen, K.P.; Klem, J.F.; Reno, J.L. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

In situ pre-growth calibration using reflectance as a control strategy for MOCVD fabrication of device structures

In situ normal incidence reflectance, combined with a virtual interface model, is being used routinely on a commercial MOCVD reactor to measure growth rates of compound semiconductor films. The technique serves as a pre-growth calibration tool analogous to the use of RHEED in MBE as well as a real-time monitor throughout the run. An application of the method to the growth of a vertical cavity surface emitting laser (VCSEL) device structure is presented. All necessary calibration information can… more

Date: August 1, 1996

Creator: Breiland, W.G.; Hou, H.Q.; Chui, H.C. & Hammons, B.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

In situ reflectance and virtual interface analysis for compound semiconductor process control

The authors review the use of in-situ normal incidence reflectance, combined with a virtual interface model, to monitor and control the growth of complex compound semiconductor devices. The technique is being used routinely on both commercial and research metal-organic chemical vapor deposition (MOCVD) reactors and in molecular beam epitaxy (MBE) to measure growth rates and high temperature optical constants of compound semiconductor alloys. The virtual interface approach allows one to extract … more

Date: May 1, 1998

Creator: Breiland, W.G.; Hou, H.Q.; Hammons, B.E. & Klem, J.F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Reflection mass spectrometry technique for monitoring and controlling composition during molecular beam epitaxy

This invention is comprised of a method for on-line accurate monitoring and precise control of molecular beam epitaxial growth of Groups III-III-V or Groups III-V-V layers in an advanced semiconductor device incorporates reflection mass spectrometry. The reflection mass spectrometry is responsive to intentional perturbations in molecular fluxes incident on a substrate by accurately measuring the molecular fluxes reflected from the substrate. The reflected flux is extremely sensitive to the stat… more

Date: August 15, 1990

Creator: Brennan, T. M.; Hammons, B. E. & Tsao, J. Y.

Item Type: Patent

Partner: UNT Libraries Government Documents Department

open access

Monolithically integrated GaAs thyristor-transistor as a hardened optically-triggered switch

Optically-triggered thyristors are hardened to high x-ray dose rates by the addition of a monolithically integrated compensating phototransistor. Tests of these devices show that sensitivity to radiation-induced switching is reduced by a factor of ten compared to conventional two-terminal thyristors (to 2 {times} 10{sup 9} Rad (Si)/sec). 3 refs., 5 figs.

Date: January 1, 1990

Creator: Carson, R. F.; Hughes, R. C.; Weaver, H. T.; Brennan, T. M. & Hammons, B. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Optically-triggered GaAs thyristor switches: Integrated structures for environmental hardening

Optically-triggered thyristor switches often operate in adverse environments, such as high temperature and high dose-rate transient radiation, which can result in lowered operating voltage and premature triggering. These effects can be reduced by connecting or monolithically integrating a reverse-biased compensating photodiode or phototransistor into the gate of the optically-triggered thyristor. We have demonstrated the effectiveness of this hardening concept in silicon thyristors packaged wit… more

Date: January 1, 1990

Creator: Carson, R. F.; Weaver, H. T.; Hughes, R. C.; Zipperian, T. E.; Brennan, T. M. & Hammons, B. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Coupled Resonator Vertical Cavity Laser

The monolithic integration of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. The authors report the first electrically injected coupled resonator vertical-cavity laser diode and demonstrate novel characteristics arising from the cavity coupling, including methods for external modulation of the laser. A coupled mode theory is used model the output modulation of the coupled resonator vertical c… more

Date: January 1, 1998

Creator: Choquette, K. D.; Chow, W. W.; Hou, H. Q.; Geib, K. M. & Hammons, B. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Wet oxidation of AlGaAs vs. AlAs: A little gallium is good

Buried oxides formed from the wet oxidation of AlGaAs alloys, rather than AlAs, are found to be superior in terms of oxidation isotropy, mechanical stability, and strain. It is not surprising that vertical-cavity surface-emitting lasers (VCSELs) using AlGaAs oxide layers as current apertures have shown promising reliability as compared to VCSELs using AlAs layers. Comparisons of lifetime data for VCSELs with differing oxide layers is presented. The beneficial properties of oxides converted from… more

Date: December 1996

Creator: Choquette, K. D.; Geib, K. M.; Hou, H. Q.; Lear, K. L.; Chui, H. C.; Hammons, B. E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Cavity structures for low loss oxide-confined VCSELs

The authors examine the threshold characteristics of selectively oxidized VCSELs as a function of the number, thickness, and placement of the buried oxide apertures. The threshold current density for small area VCSELs is shown to increase with the number of oxide apertures in the cavity due to increased optical loss, while the threshold current density for broad area VCSELs decreases with increasing number of apertures due to more uniform current injection. Reductions of the threshold gain and … more

Date: May 1997

Creator: Choquette, K. D.; Hadley, G. R.; Chow, W. W.; Hou, H. Q.; Geib, K. M.; Hammons, B. E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Composite resonator vertical cavity laser diode

The use of two coupled laser cavities has been employed in edge emitting semiconductor lasers for mode suppression and frequency stabilization. The incorporation of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. Composite resonators can be utilized to control spectral and temporal properties within the laser; previous studies of coupled cavity vertical cavity lasers have employed photopumped … more

Date: May 1, 1998

Creator: Choquette, K. D.; Hou, H. Q.; Chow, W. W.; Geib, K. M. & Hammons, B. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Selectively oxidized vertical-cavity laser performance and technology

The authors discuss revolutionary performance advances in selectively oxidized vertical-cavity surface emitting lasers (VCSELs), which have enabled low operating power laser diodes appropriate for aerospace applications. Incorporating buried oxide layers converted from AIGaAs layers within the laser cavity produces enhanced optical and electrical confinement enabling superior laser performance, such as high efficiency and modulation bandwidth. VCSELs also shown to be viable over varied environm… more

Date: February 1, 1998

Creator: Choquette, K. D.; Hou, H. Q.; Geib, K. M. & Hammons, B. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Threshold properties of a microcavity laser with submicroampere threshold current

We report the threshold characteristics of small oxide-confined vertical-cavity surface emitting lasers. Abrupt threshold transitions 105 times the spontaneous emission background are obtained at injection currents as low as 470 nanoampere.

Date: February 1, 1996

Creator: Choquette, K. D.; Hou, H. Q.; Lear, K. L.; Chow, W. W.; Mar, A.; Geib, K. M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Stimulated emission from semiconductor microcavities

Laser-like emissions from semiconductor microcavities at low temperature have attracted considerable attention recently because of the possibility of realizing a non-equilibrium condensate by using cavity-polaritons. In this paper the authors present experimental studies of optical properties of a microcavity near the lasing threshold. They show that the minimum lasing threshold is achieved when the cavity is tuned significantly below the exciton line center. By comparing emission spectra with … more

Date: April 1, 1997

Creator: Fan, X.; Wang, H.; Hou, H.Q. & Hammons, B.E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Fabrication issues of oxide-confined VCSELs

To insert high-performance oxide-confined vertical-cavity surface- emitting lasers (VCSELs) into the manufacturing arena, we have examined the critical parameters that must be controlled to establish a repeatable and uniform wet thermal oxidation process for AlGaAs. These parameters include the AlAs mole fraction, sample temperature, carrier gas flow, and bubbler water temperature. Knowledge of these parameters has enable the compilation of oxidation rate data for AlGaAs which exhibits an Arrhe… more

Date: April 1, 1997

Creator: Geib, K. M.; Choquette, K. D.; Hou, H. Q. & Hammons, B. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Uniformity and performance of selectively oxidized VCSEL arrays

The authors report the uniformity characteristics of low threshold 1,060 nm and high power 850 nm 8 x 8 individually addressable oxide-confined VCSEL arrays. Uniformity of lasing thresholds and operating characteristics are described, as well as thermal issues for 2-dimensional laser arrays.

Date: January 1, 1998

Creator: Geib, K. M.; Choquette, K. D.; Hou, H. Q. & Hammons, B. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Mirror reflectivity and doping considerations for high performance oxide-confined vertical cavity lasers

We report the effects of mirror doping and reflectivity in 850 and 780 nm oxide-confined vertical cavity surface emitting lasers. Decreased doping throughout the n-type mirror produces significantly higher quantum efficiency, while the optimum reflectivity is dependent upon the gain material.

Date: January 1, 1996

Creator: Geib, K.M.; Choquette, K. D.; Chui, H. .; Hou, H. Q. & Hammons, B. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Surface-emitting superconductor laser spectroscopy for characterizing normal and sickled red blood cells

We have developed a new intracavity laser technique that uses a living or a fixed cell as an integral component of the laser. The cells are placed on an AlGaAs/GaAs surface-emitting semiconductor wafer and covered with a glass dielectric mirror to form a laser resonator. In this arrangement, the cells serve as optical waveguides (or lens elements) to confine (or focus) light generated in the resonator by the semiconductor. Because of the high transparency, the cells aid the lasing process to ge… more

Date: February 1, 1995

Creator: Gourley, P. L.; Meissner, K. E.; Brennan, T. M.; Hammons, B. E. & Gourley, M. F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Characterization of semiconductor surface-emitting laser wafers

The development of epitaxial semiconductor surface-emitting lasers has begun in recent years. These lasers are ultra-short (few {mu}m) Fabry-Perot resonators comprising epitaxial multilayer semiconductor mirrors and quantum well active regions. The resonators are single crystals grown along the lasing axis by molecular beam epitaxy (MBE) or chemical vapor deposition (CVD). They offer significant advances over conventional cleaved, edge-emitting lasers for creating lasers with single elements of… more

Date: January 1, 1990

Creator: Gourley, P. L.; Vawter, G. A.; Brennan, T. M. & Hammons, B. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department